We propose that pheromones (chemicals secreted from animals that cause behavioral responses among other animals of the same species) play an essential role in the premating behavior of various zooparasitic nematode species. Especially, such chemicals may be essential for individuals of one sex to be able to locate the opposite sex prior to mating. We will investigate biological and chemical aspects of pheromone communication in two species, Nippostrongylus brasiliensis and Trichinella spiralis. The role of the pheromones in stimulating various premating behaviors will be determined in laboratory cultures, and the influence of a number of physiological and environmental factors in controlling and modulating the pheromone communication system will be elucidated. Quantitative bioassays for the pheromones will be designed, based on the results of these studies. Chemical investigations will be directed toward the isolation, purification, and ultimate identification and synthesis of the pheromone chemicals. Exploratory studies will be directed toward investigation of the effect of primer pheromones in accelerating maturation, synchronizing or inhibiting development, or causing other physiological effects in nematodes of the same species or in other species. Finally, experiments will be designed to provide hypotheses concerning the potential practical usefulness of pheromones as pharmaceutical agents for disease control.